Impact absorbing structures are disclosed in, for example, Japanese Patent Application, Second Publication, H5-410, Japanese Utility Model Application, First Publication, H3-13251, Japanese Patent Application, First Publication, H3-49110 and Japanese Patent Application, First Publication, H3-49111, which are based on styrene or urethane foams disposed at certain strategic locations within a passenger automobile.
The type of construction used in these conventional impact absorbing structures is based on encasing impact absorbing members in plastic parts. Because of such dual structures, the final cost of the impact absorbing structures is high, and their assembly steps are also increased.
An approach to remedy such a problem is disclosed in documents such as Japanese Patent Application, First Publication, H4-128912, and Japanese Patent Application, First Publication, H6-72153 which disclose a structure in which plastic rib members themselves act as impact absorbing structural members.
However, the characteristics required for impact absorbing members should be different for different applications, and these publications do not disclose any specific designs for the rib structures to judge whether the impact absorbing structures can be customized to suit the conditions encountered in their applications.